Monomeric epoxides contain small quantities of impurities containing active hydrogen which must be removed to prepare polymers with molecular weights above 20,000. The impurities when present even in a few ppm range slow the polymerization rate by a factor of 10 or more.
The usual impurities include glycols, alcohols and traces of water. Prior art procedures for purifying epoxides have included the addition of calcined KOH or CaH.sub.2 and then distilling. However, KOH and CaO are known polymerization initiators, so that during distillation, explosive polymerizations can take place. Even under the most careful operating conditions, when using prior art procedures, removal of all impurities is difficult. Failure to remove these impurities makes it very difficult to make polymers having a molecular weight above 20,000 with any degree of consistency.
It is apparent, therefore, that a method by which impurities can be removed or made innocuous is highly desirable.
We have found a simple, yet very effective, method for purifying monomeric epoxides, to provide monomers which homo- or copolymerize rapidly, substantially completely, and produce high molecular weight polymers consistently. The epoxides are particularly useful for forming block copolymers of the structure ERE where R is a hydrocarbon chain and each E represents a polyether group derived from an epoxide.